This post is to get some opinions, and hopefully I may receive some responses that will put my mind at ease. We are a development house who have been building on DNN for many years and have put out some great solutions. We are now in the process of selling a stake in our business to a company who have for many years used the LAMP stack for everything.

They want to invest in us because of our skills in general as web professionals and not necessarily for .NET or DNN skills; however, .NET and Microsoft (as many would know) continuesly gets a bad wrap from the other open source communities as being to slow, too bloated and just plain uncool compared to other platforms written in Drupal or any framework that is not .NET

I do however feel that DNN is great, but currently has the following important achilles heel; 1) it is still much slower than most other frameworks and 2) it is not SEO friendly out of the box, or at least not as good as a few other frameworks. (You require URL master and some other "hacks" to have nice cleanly formatted URL).

The URL thing is becoming more and more of a "coolness" thing it would seem. In the end you just want to get the job done and the clients wants a good ROI, but the battle between technology choices will continue to rage on like discussing politics and religion.

Not going to happen.  There is no better or worse development environment.  A solution is only better or worse than another for a particular problem.  Define the problem, then find the correct solution.

Jeff